The present invention relates to a novel data collection system for remote reading of the readings of meters each installed for each consumer into a metering center or station in order to compute the consumption of city or town water, gas or electricity.
A variety of systems for permitting a central metering station or metering center to read the indications or readings of a large number of electric, water and gas meters remotely installed each for each consumer have been devised and demonstrated. From the view point of the data transmission methods they may be divided into a system utilizing a power transmission line, a system utilizing a telephone net work and a system utilizing a cleared channel. The present invention relates to the last mentioned system utilizing the cleared channel, and various data collection systems utilizing the cleared channels have been devised and demonstrated.
However, none of them has been successful in practice because the transmission lines interconnecting between the metering center and a large number of terminal equipments such as meters are prohibitively greater in numbers and further because the erroneous selection of more than two terminal equipments tends to occur very frequently. In one type of data collection system each terminal equipment is provided with a decoder to respond a calling or selection signal transmitted from the metering center so that the terminal equipment may be electrically connected to the center. However, the semiconductor elements incorporated into the decoders are frequently subjected to high surge voltages due to thunderbolts or the like and are broken so that the erroneous selection more than two terminal equipments tends to occur very often as described above. The present invention was made to solve the above and other problems encountered in the prior art remote data collection system and is based on the underlying principle that the terminal equipments may be connected to the metering center without the use of the conventional decoders incorporated in the terminal equipments for the selection thereof.